The three numbers Google actually measures
Core Web Vitals are Google's attempt to measure what a website actually feels like to use, rather than just how it looks. There are three of them, and they're worth knowing even if you never touch the technical side yourself:
- Largest Contentful Paint (LCP): how long it takes for the main content of a page to actually appear. Good is under 2.5 seconds.
- Cumulative Layout Shift (CLS): whether things jump around while the page loads (that moment you go to tap a button and an image loads above it, shoving everything down). Good is under 0.1.
- Interaction to Next Paint (INP): how quickly the page responds once someone actually clicks or taps something. Good is under 200 milliseconds.
For years, INP sat in the background as a secondary metric. That changed this year.
Why INP matters more than it used to
Google's March 2026 core update formally moved INP up to sit alongside LCP and CLS as a primary ranking signal, not a nice-to-have. In practical terms, a site that loads fine but feels laggy when you tap a menu or submit a form is now being marked down for that laziness specifically, separate from how fast it initially loaded.
That distinction matters because a lot of older, template-heavy websites load acceptably but respond poorly. Heavy JavaScript, bloated plugins, and third-party scripts (chat widgets, tracking pixels, ad scripts) are usually the culprits. The page finishes loading, then sits there being slow to react every time someone actually tries to use it.
Sites sitting in the "needs improvement" range for INP have been seeing measurable ranking drops on competitive search terms, and the businesses feeling it most are the ones who assumed a fast-loading homepage meant they'd already ticked the speed box.
Why this isn't just an SEO story
Here's the thing about Core Web Vitals: they're not really a Google trick to game. They're Google measuring something real, whether your website is pleasant to use on a phone with an average connection, standing in a car park, one thumb free. A site that scores badly on INP isn't just losing search position. It's frustrating actual customers who came to book, call, or buy something and gave up because the button took a beat too long to respond.
We treat Core Web Vitals as a symptom, not the disease. If your INP is bad, something specific is causing it: too many plugins doing too much on every page load, images that aren't properly sized, third-party scripts you added once and forgot about. Fixing the underlying cause improves the metric and the experience at the same time.
What's worth checking on your own site
- Run your homepage and one or two key service pages through Google's PageSpeed Insights (free, takes thirty seconds) and look specifically at the INP number, not just the overall score
- If you're on WordPress, audit your plugins. Every plugin you're not actively using is dead weight slowing down every single page
- Check whether you've got chat widgets, review pop-ups, or tracking scripts stacked up from services you tried once and never removed
- If your site was built more than three or four years ago and hasn't had a technical refresh since, it's worth an honest look. A lot of the "just add another plugin" fixes from that era are exactly what's dragging INP down now
None of this requires a full rebuild in most cases. It usually requires someone who knows what to look for spending an hour going through the site with the right tools. That hour tends to pay for itself pretty quickly once you're not losing ranking positions to a slow tap response.